We snap a selfie with the tap of a finger. We're used to preserving smiling moments.

At the Museum of Contemporary Art in Los Angeles, there's an exhibit right now which goes to darker places with a camera. The images in "Real Worlds" are from three major photographers, taken over half a century.

There's Brassaï, a French-Hungarian who made his reputation revealing secret Paris nights between the World Wars. There's Diane Arbus, American, who said in the 1960s, "I really believe there are things nobody would see if I didn't photograph them." And there's Nan Goldin, another American, who stunned the 1980s with her series "The Ballad Of Sexual Dependency."

All three picture-takers are revolutionary: They photographed, with profound intimacy, the undersides of life. Their images are stunning, sometimes shocking, often provocative.

In nighttime Paris, Brassaï stalked the underworld — brothels, streetwalkers. But at MOCA, there's a Brassaï shot of a happy night at an Afro-Caribbean club in Montmartre. Black and white people smoke together, sip Perrier or stronger stuff, dance. And there's an intriguing woman on the left.

"She's wearing this white hat that's just off to the side, a kind of kerchief hat, and she's staring directly at the camera," says curator Lanka Tattersall. "And this is the thing that I find so remarkable in this image. It's taken in 1932. She's looking at Brassaï and she's very aware of her image being taken by this photographer."

It didn't happen that much in 1932 — people roaming around, unannounced, taking your picture. What might she have been thinking?

"She's probably thinking — you know, this scene is being preserved," Tattersall says. "I think that's what makes this photograph absolutely contemporary, is an awareness of what it is to be photographed, and to really think about having your image distributed across time and space."

Thirty years later, American photographer Diane Arbus inherited Brassaï's vision. We were used to having our pictures taken by the 1960s. But Arbus' focus was new. In black and white, she documented people on the fringes. Giants, bearded ladies, people with mental disabilities or those who may have been institutionalized. In Tattersall's words: "people whose bodies or sexual identities didn't conform with kind of mainstream narrative of what it was to be an American."

Arbus was accused of voyeurism, of going after what were then called freak shows. But Tattersall, the MOCA curator, says Arbus forged relationships with her subjects, and that there's empathy in the pictures.

"And it's just this person lying alone, on a bed," Tattersall says. "She's got some balloons taped up on the wall. It might just be a two-person birthday party. It might just be Arbus and this one woman. They're having a fabulous time."

Transgender people also intrigue photographer Nan Goldin. Twenty years after Arbus, Goldin photographs them — as well as gays and lesbians. Hers are the most provocative pictures in the MOCA exhibit.

She also shows people having sex — friends, who let her photograph them having sex. Her camera is part of their scene. Are the pictures invasive?

"I think they're voracious," Tattersall says.

Goldin is exploring relationships — what happens in love, and when love goes wrong. Her 1984 self-portrait, "Nan one month after being battered" (pictured atop this page) shows the damage her lover did to her. Dark bruises under her eyes — the left eye bloody in her swollen face — she looks right at us. The look is uncompromising.

"I think there's a chilling way in which she's saying, 'This is what it looks like to be battered,'" Tattersall says. "But this is also what it looks like to take control of your own image."

Nan Goldin was 31 years old in that photo. One battered eye was nearly blind. But she's painted her lips carefully. A bright, bright red.

"Even if that moment of violence and abuse is one of victimization, there's a way in which she's saying, "'I am taking my own agency back in this image,'" Tattersall says.

There's a lot of rough stuff in this exhibition — images and ideas that linger long after you've left the building. They trace how great photographers have used their cameras to make us see, understand or recoil, in the course of half a century.

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NOEL KING, HOST:

Photographs taken over the course of 50 years are on view in Los Angeles. Three different photographers captured stunning and shocking and provocative images. And then a curator at the Museum of Contemporary Art found connections among the pictures. NPR's special correspondent Susan Stamberg explains.

SUSAN STAMBERG, BYLINE: We snap a selfie with the tap of a finger. We're used to preserving smiling moments. The MOCA show goes to darker places with the work of three major photographers - Brassai, a French-Hungarian who made his reputation revealing secret Paris nights between the wars, Diane Arbus, American, who said in the '60s, I really believe there are things nobody would see if I didn't photograph them, and Nan Goldin, another American, who stunned the 1980s with her series "The Ballad Of Sexual Dependency." All three picture takers are revolutionary, photographing with profound intimacy the undersides of life.

(SOUNDBITE OF MUSIC)

STAMBERG: In nighttime Paris, Brassai stalked the underworld - brothels, streetwalkers - but at MOCA, a happy night at an Afro-Caribbean club in Montmartre. Blacks and whites smoke together, sip Perrier or stronger stuff, dance.

LANKA TATTERSALL: They're having a great time. And then there's this one woman on the left-hand corner that I just find so striking.

STAMBERG: Curator Lanka Tattersall.

TATTERSALL: She's wearing this white hat that's just off to the side, a kind of kerchief hat, and she's staring directly at the camera. And this is the thing that I find so remarkable in this image. It's taken in 1932. She's looking at Brassai, and she's very aware of her image being taken by this photographer.

STAMBERG: It didn't happen that much in those days, people roaming around unannounced, taking your picture.

TATTERSALL: She's probably thinking, you know, this scene is being preserved. I think that's what makes this photograph absolutely contemporary, is an awareness of what it is to be photographed and to really think about having your image distributed across time and space.

STAMBERG: Thirty years later, American photographer Diane Arbus inherited Brassai's vision. We were used to having our pictures taken by the 1960s, but Arbus' focus was new. In black and white, she documented people on the fringes - giants, bearded ladies, also...

TATTERSALL: People with mental disabilities, people who may have been in institutions, people whose bodies or sexual identities didn't conform with kind of mainstream narrative of what it was to be an American.

STAMBERG: She was accused of voyeurism, going after what were then called freak shows. But the MOCA curator says Arbus forged relationships with her subjects. Lanka Tattersall sees empathy in these pictures.

TATTERSALL: To me, she's photographing these remarkable individuals who want to be photographed.

STAMBERG: There's an amazing 1969 photo Arbus called "Transvestite At Her Birthday Party."

TATTERSALL: And it's just this, you know, person lying alone on a bed. She's got some balloons tacked up on the wall. It might just be a two-person birthday party. It might just be Arbus and this one woman. They're having a fabulous time.

STAMBERG: Transgender people also intrigue photographer Nan Goldin. Twenty years after Arbus, Goldin photographs them and gays, lesbians. Hers are the most provocative pictures in the MOCA exhibit. She shows people having sex - friends who let her photograph them having sex. Her camera is part of their scene. Are the pictures invasive?

TATTERSALL: I think they're voracious.

STAMBERG: She's exploring relationships - what happens in love and when love goes very wrong. Her self-portrait, "Nan After Being Battered (ph)," 1984, shows the damage Goldin's lover did to her - dark bruises under her eyes, the left eye bloody in her swollen face. She looks right at us. The look is uncompromising.

What do you see in that face? Is it anger, revenge?

TATTERSALL: I think there's a chilling way in which she's saying, this is what it looks like to be battered, but this is also what it looks like to take control of your own image.

STAMBERG: Nan Goldin was 31 years old in that photo. One battered eye was nearly blind, but - and - she's painted her lips carefully a bright, bright red.

TATTERSALL: Even if that moment of abuse is one of victimization, there's a way in which she's saying, I am taking my own agency back in this image.

STAMBERG: A lot of rough stuff in this exhibition at the Museum of Contemporary Art, Los Angeles - images and ideas that linger long after you've left the building. They trace how great photographers have used their cameras to make us see, understand or recoil in the course of half a century. In California, I'm Susan Stamberg, NPR News. Transcript provided by NPR, Copyright NPR.